In a paper conveying apparatus of an image reading apparatus, printing apparatus, etc., sometimes a plurality of sheets of paper are conveyed on the conveyance path in a superposed state, that is, multifeed occurs.
An image reading apparatus which sends an ultrasonic wave toward paper of a document being conveyed and determines that a multifeed has occurred when the level of reception of the ultrasonic wave which passes through the paper of a document is a predetermined threshold value or less has been disclosed (see Japanese Laid-open Patent Publication No. 2009-161291).